I currently have a water boiler where the inlet water is about 6C (43F) while in my country the average temperature is 15C.
I want to use the outdoor temperature just warm the water instead of heating it before it reaches my boiler. 50-100L storage would be enough for me. I was thinking of just having a tank with an inlet or outlet. I still want to keep the original pressure.
Is this possible to make yourself or are there any complete solutions to buy? I google but could not find anything. My budget is probably around €200/$200.